Research On Chlorosilane Residual Liquids Preparation Of Silica And By-product Hydrochloric Acid Hydrolysis Process

In the condition of fossil energy constraints and unbearable environment, solar energy as a renewable energy is increasingly brought to the attention of the people, the demand of polycrystalline silicon has sharply growed, which is an important industrial raw material for the solar industry. Most of polysilicon production enterprises in China has yet to grasp the core of polysilicon production technology, their technology and equipment are backward, they are unable to realize closed-loop production of improved Siemens method. Polysilicon production process every production output 1 t will produce about 10 t of chlorosilane residual liquids, so chlorosilane residual liquid recycling problem has become the constraints of a bottleneck in the development of polysilicon industry.Based on good chemical stability, high temperature resistant, not burning, good electrical insulation properties of silicon dioxide, and its application scope is wide, This paper explore a new technology to use chlorosilane residual liquids to product silicon dioxide byproduct hydrochloric acid hydrolysis. It can recycle hydrolysis to produce silica as a product and recycle concentrated hydrochloric acid. We mainly studied the different hydrolysis methods and product positioning, hydrolysis reactor design, process parameter optimization of enlarge experiment, the product performance.Firstly by exploring hydrolysis methods influence on the properties of silicon dioxide and hydrochloric acid concentration, the results show that chlorosilane residual liquid with water or hydrochloric acid reaction can enrich hydrochloric acid, and circulating leaching tower reactor is the most suitable, the product positioning is precipitated silica. At the same time, combined with the experimental results the whole chlorosilane residual liquid hydrolysis process was confirmed. Secondly this paper has designed a continuous loop hydrolysis reactor, including hydrolysis tower and intermediate collection trough. Hydrolysis tower of enlarge experiment device has diameter of 200 mm,5 m high, the size of intermediate collection trough is φ 1.5m* 1.2m. Finally, optimize parameters of hydrolysis reactor, the optimal operating parameters:the circulation amount of absorbing liquid is 750 L/h, nitrogen gas flow is 7.5m3/h, the chlorosilane residual liquid flow is 9 L/h. And hydrolysis efficiency can reach above 99%, at the same time hydrochloric acid can be successfully enriched.The study on product performance shows that the phase structure, radical group, morphology, impurity content of silica products accord with performance of precipitated silica as rubber reinforcing agent. At the same time the product has good thermal stability, under 1000 ℃ crystal shape can’t change. Although particle size of silica product is in the range of 50-80 um, residual acid value (pH) is 2.17,they cannot accord with HG/T 3061 2009,but the optimized process parameters can solve the problem of particle size and the residual acid sub-standard.